LB FILMS OF POLYSILOXANES FOR 2ND-HARMONIC GENERATION

Azo dye chromophores with acceptors of increasing strength have been s ynthesised. They were studied as LB film forming materials both as mon omers with C18H37 tails and attached to polysiloxane backbones with C6 H12 spacer groups. The polymers were much superior to the monomers as LB materials; they were screened as deposited monolayers for SHG effic iency, which was found to increase with the acceptor strength. The bes t film forming material is a previously-reported polymer which has no acceptor group; it exhibits a soft crystalline phase which may have a bearing upon its exceptional film-forming properties which result in m um thick optically-clear films. It exhibited SHG only on deposition fr om an acid subphase. The maximum SHG efficiency so far observed in any of these materials is about 0.1 of that of Hemicyanine. Properly opti mised, these materials may be usable for non-linear waveguiding.